THE SIR SUPPLIED DR. LEWIS WITH .5G OF L-[3'-5'13C2] TYROSINE & .5G OF L-[1,5-13C2] GLUTAMATE SPIDER DRAGLINE SILK IS THE STRONGEST MATERIAL YET TESTED, NATURAL OR MANMADE. IT HAS A TENSILE STRENGTH GREATER THAN 200,000 PSI AND AN ELASTICITY GREATER THAN 30%. THESE VALUES EXCEED THOSE OF STEEL AND NYLON RESPECTIVELY. YET THE FIBER IS FORMED FROM AN AQUEOUS SOLUTION AT AMBIENT TEMPERATURES AND PRESSURES. WE ARE THE FIRST AND ONLY GROUP, TO DATE, TO HAVE CLONED THE TWO PROTEINS WHICH MAKE UP THIS FIBER. THESE PROTEINS, WHICH ARE COMPOSED OF AN IN EXACTLY REPEATING UNIT COMPOSED OF TWO DIFFERENT TYPES OF SEQUENCES, HAVE NO SUBSTANTIAL SEQUENCE HOMOLOGY WITH ANY OTHER PROTEIN IN THE CURRENT SEQUENCE DATABASE. BASED ON THESE SEQUENCES, FTIR, CD AND NMR STUDIES WE HAVE PROPOSED A STRUCTURE FOR THESE PROTEINS. WE CALL IT THE LEGO-SLINKY MODEL WHERE A POLY-ALANINE REGION IS IN A CRYSTALLINE-LIKE STRUCTURE WITH THE METHYL GROUPS SEQUESTERED IN A *-SHEET WHICH GENERATES THE TENSILE STRENGTH. THE OTHER REPEAT REGIONS FORM *-TURN SPIRALS AND CAN EXTEND REVERSIBLY TO PROVIDE ELASTICITY. IN ORDER TO TEST THESE STRUCTURES WE WILL HAVE TO USE STABLE ISOTOPE LABELED PROTEINS AND SOLID STATE NMR, AS THE SOLUTIONS STRUCTURES ARE NOT RELEVANT TO THE FIBER STRUCTURE. WE HAVE NOW SUCCESSFULLY INCORPORATED C-13 LABELED GLYCINE AND ALANINE INTO THE SPIDER SILK BY FEEDING SPIDERS THE LABELED AMINO ACIDS IN WATER. HOWEVER, THE KEY AMINO ACIDS IN OUR STUDY ARE PROLINE, GLUTAMINE AND TYROSINE WHICH ARE INVARIANT IN ALL REPEATS ANT THUS MUST PLAY KEY STRUCTURAL ROLES. WE PLAN TO LABEL THE SPIDER SILK IN THE SAME MANNER AS WE HAVE THE OTHER AMINO ACIDS AND COLLECT THE SILK. THE SAMPLES WILL BE ANALYZED USING SOLID STATE NMR USING ROTATIONAL RESONANCE AND REDOR METHODS TO DETERMINE THE DISTANCES BETWEEN NUCLEI AND TO CONFIRM OR ADJUST OUR WORKING MODEL.